DE3224339A1 - Process and apparatus for separation of hydrogen or helium from gas mixtures - Google Patents

Abstract

In a process for the separation of hydrogen or helium from gas mixtures using a cooling stage system, the gas to be separated and also nitrogen, oxygen and/or gases having about the same boiling range being contained in the mixture, the gas mixture is cooled in at least two, preferably three cooling stages (2,6,15) to about 60-70 K for condensation of the higher-boiling gases. The condensation of the higher-boiling gases can take place at an operating pressure of 150-250 bar or 10-50 bar. At an operating pressure of 10-50, preferably 20 bar, the remaining gas mixture is subjected to a fine purification in a subsequent adsorption trap (53,54). Two or three cooling stages (2,6,15) are provided for performing the process, and are constructed such that the temperature of the product gas in the last stage is 60-70 K, preferably 63 K. <IMAGE>

Description

Method and device for separating hydrogen

or helium from gas mixtures. The invention relates to a method for the separation of hydrogen or helium from gas mixtures using a Cooling stage system, with the gas to be separated as well as nitrogen and oxygen in the mixture and / or gases from approximately the same boiling range are included. Also relates the invention relates to a device suitable for carrying out the method.

The separation of helium or hydrogen from gas mixtures with the help a precondensation stage or a cooling stage and adsorption traps known for operating pressures between 100 and 250 bar. These processes are economical but only if the operating pressure has the relatively high values mentioned and an adsorption trap is connected downstream for fine cleaning. With the previously known In addition to the costly, processes are therefore costly in order to achieve reasonably good results designed adsorption traps still require expensive compressors.

The object of the present invention is therefore to provide a method of type mentioned at the beginning as well as a suitable one for the implementation of this method To create device in which an economy or improvement also is still given at relatively low operating pressure or at those at high operating pressure only small adsorption traps or no adsorption traps at all required are.

According to the invention this object is achieved in that the gas mixture in at least two, preferably three cooling stages to about 60 to 70 K is cooled for the purpose of condensation of the higher-boiling gases. An essential one The advantage of this method is that it can be used even at low operating pressures and delivers good results without downstream adsorption traps. The product gas yield is 99 to 100%. Even with high concentration and / or throughput fluctuations The process can be used in the starting gas mixture. Gases in the same boiling range such as nitrogen and oxygen, such as B. carbon monoxide, argon and the like. Can This process can also be used to separate hydrogen or helium.

An improvement in the final purity up to 1 vpm residual contamination can be achieved economically either by having the condensation of the higher boiling gases at higher operating pressures, e.g. B. 150 to 250 bar, takes place or in that the condensation of the higher boiling gases at an operating pressure of 10 to 50 bar, preferably 20 bar, and that the remaining gas mixture in a downstream adsorption trap is subjected to fine cleaning. at this process can either be based on elaborate adsorption traps or expensive high-pressure compressors with high energy consumption can be dispensed with.

Further advantages and details of the invention are based on a are explained in the figure schematically illustrated flow chart.

The illustrated embodiment is initially for the separation of hydrogen from a hydrogen-nitrogen mixture with high nitrogen pollution certainly.

This mixture is fed to a first cooling stage 2 at 1.

Is there still oxygen, carbon dioxide or water vapor in the mixture to be cleaned included, then cooling level 2 expediently another one Pre-cleaning stage, not shown, is connected upstream, in which the oxygen is catalytically is burned into water. For the removal of water vapor and / or carbon dioxide a zeolite adsorption bed is to be connected upstream of cooling stage 2, in which this Fractions are adsorbed. In the case of the separation of helium from a helium-nitrogen-oxygen mixture all that is required is pre-drying. The removal of oxygen before the separation according to the invention is unnecessary.

The cooling stage 2 with its coils or cooling registers 3, 4 and 5 is operated in countercurrent and is designed so that the oil-free in advance on a Pressure between 10 and 50 bar, preferably 20 bar, brought gas mixture of room temperature is cooled to 130 to 100 K. According to the percentage of the volume of hydrogen and nitrogen in the gas mixture to be separated is the corresponding one Partial pressure for hydrogen and nitrogen.

If the partial pressure of nitrogen is above the vapor pressure of 130 or 100 K, partial liquefaction of the occurs in the first cooling stage 2 Nitrogen up to the respective vapor pressure.

Thereafter, the remaining gas mixture reaches the cooling stage 6 as Dewar vessel is formed. It includes a cooling coil 7 in an LN2 bath # 8. The cold vapors from this bath are fed to cooling stage 2 via line 9 and flow through the coil 3 in countercurrent to the gas mixture supplied. The preferably The evacuated isolation space of the Dewar vessel is denoted by 10.

The cooling stage 6 is equipped with a level sensor 11, which is on the valve 12 acts regulating. Nitrogen losses are avoided by opening the valve 12 from the storage vessel 13 refilled. This storage vessel 13 contains liquid nitrogen under a pressure of preferably 1.5 bar.

A pressure of 1.3 to 1.4 is achieved in the steam space 14 of the Dewar vessel 6 bar upkeep. This results in a liquid temperature of approx. 80 No. The length of the cooler or the coil 7 is dimensioned so that the to be separated Gas mixture leaves cooling stage 6 at a temperature of approx. 83 K.

When a mixture of z. B. 10 Nm / h hydrogen and 10 Nm3 / h Nitrogen and a total pressure of 20 bar are 3 of the 10 Nm / h nitrogen in cooling level 6 approx.

8.3 Nm3 / h nitrogen liquefied. It therefore remains in the cooling stage 6 leaving gas mixture approx.

1.7 Nm3ih. Based on the 10 Nm ih gaseous mixture of nitrogen components before the second cooling stage 6, the separation efficiency in this cooling stage is approx. 82.5 Z. Behind cooling level 6 there are still 1.7 Nm3ih, i.e. approx.

Contains 17.5%, gaseous nitrogen.

From the second cooling stage 6, the remaining gas mixture passes into a third cooling stage, which is generally designated by 15. In this cooling stage 15 the mixture is brought to a temperature of approx. 65 K and so is the remaining one liquefied gaseous nitrogen from 1.7 Nm3 ih to X.2 Nm3 / h of gaseous nitrogen. Based on the 1.7 Nm³ / h of gaseous nitrogen from the second cooling stage 6 is the separation performance of the third cooling stage 15 88.3 Z.

In order to achieve these values, the cooling stage 15 consists of a vessel 16 with a central insert 17. This forms an annular space 18 in which there is again a bath with liquid nitrogen and in which the cooler resp. the cooling coil 19 is housed. The one in cooling levels 6 -u = r £ d -15. Nitrogen content that has become liquid flows into the below cooling stage 15 located storage container 21, -in.d-eat gas space 22 of the cooler or the cooling coil 19 ends.

--De.t # Gas space 23 of nitrogen bath 18 is available via line 24 in connection with a vacuum pump-2S. By means of this vacuum pump 25, the vapor space 23 kept continuously at a pressure of about 130 mbar, which is a vapor pressure of 63 K. This results in a bath temperature of approx. 6 = 5 K, whereby the cooling of the gas mixture to be separated to 65 K can be provided.

The container 21 is normally - i. H. with sufficient nitrogen content in the starting gas mixture - a relatively large amount of nitrogen is constantly supplied. That's why knows how to supply cooling stages 15 and 6 with this nitrogen will. Liquid nitrogen is supplied by means of the level sensor 26 and valve 27 is pressed via the line 28 into the container 29 and there from the in the container 21 the prevailing 20 bar is relaxed to 1.4 bar. The liquid comes out of the container 29 Nitrogen via line 31 to cooling stages 15 and 6th level sensor 32 and valve 33 regulate the supply to cooling stage 15. The regulation of the supply of liquid nitrogen for cooling stage 6 depends on the liquid level in the container 29. There is also the level sensor 34 is provided, which controls the valve 35 in the line 31. This regulation has the Advantage that the supply of the cooling stage 15 with liquid nitrogen from the container 29 always has priority over the supply of cooling stage 6 from this container 29. The pressure sensor 36 regulates the valve 37 in the exhaust line 38 such that the pressure of 1.4 bar in the container 29 is maintained.

If the nitrogen content in the starting gas mixture is very low, the The cooling stage 15 is also supplied from the storage container 13. In addition is the below the Level sensor 32 lying further level sensor 41 which controls the valve 42 is provided. When the valve 42 is open, the annular space 18 is connected to the liquid bath via the line 43 with the storage container 13.

The cooling stage 15 as well as the containers 21 and 29 are inclusive the associated control devices to avoid cold losses in a box 44 housed, to which also the isolation room 10 designed as a Dewar vessel Cooling level 6 is connected. By means of the diffusion pump 45 and the backing pump 46 the inside of the box 44 is constantly kept at a pressure of about 10 5 mbar, whereby the cold losses are further reduced.

The remaining gas mixture emerges from the gas space 22 of the container 21 into the central insert 17 of the cold stage 15. This central mission is with Filled fillings (e.g. copper saddle), which are also removed from the cooling bath 18 to approx. 65 K are held.

Liquid particles entrained in the gas mixture are removed from the packing deposited and drip back into the container 21. As a result of the packing and as a result this reflux of liquid nitrogen results in a further separation of gaseous nitrogen from the gas mixture. The separation efficiency of this column is because of the large difference between the nitrogen and hydrogen boiling temperatures and the expected low return low. Since, however, with fluctuations in throughput of the starting gas mixture and different flow velocities in the case of fluctuations in concentration and thus under different performances in the cooling level 15 can occur the resulting deteriorated separation performance of the cooling stage 15 at least partially of the Packed column to be balanced, as the separation efficiency this column gets better with increasing nitrogen concentration.

The remaining gas mixture leaves the interior of the cooling stage 15 the line 47 and is - controlled by the valves 48 and 4-9 - alternately the low temperature adsorption traps 51 and 52 are supplied. In these with activated charcoal or molecular sieve-filled traps, the remaining gaseous nitrogen - up on the residual contamination of 1 vpm still present afterwards - removed. The activated carbon or the molecular sieve are housed in containers 53, 54, which are to be cleaned Gas mixture are flowed through from bottom to top. The separated hydrogen leaves the system via lines 55 and 56 with valves 57 and 58 and via the Cooler or the cooling coil 5 in the first cooling stage 2. From the cooler or the cooling coil 4 of the cooling stage. 2 inflowing starting gas mixture is the hydrogen brought to about room temperature. The adsorption traps 53, 54 receiving Containers are again designed as Dewar vessels, each with a bath from liquid nitrogen (61, 62) is located. By means of the level sensors 63, 64, the controlled valves 65, 66 and the lines 67, which lead to the storage vessel 13, control of the baths takes place in the adsorption traps 51, 52. As a result, the bath has a temperature of about 80 K. However, since the inflowing product gas has a temperature of approx. 65 K, the operating temperature is within the containers 53 and 54 lower, to about 70 K.

The adsorption traps 51 and 52 are operated alternately in such a way that that while one trap is in operation, the other is regenerated and vice versa. For regeneration, the liquid nitrogen must first be removed from the respective bath removed will. This can be done by means of the immersion heaters 68 and 69 shown schematically happen. The nitrogen gas flows through the lines 71 and the check valve 72 off. Instead of or in addition to the immersion heaters 68, 69 ', one can also be used Pressurized gas source, not shown, can be provided, by means of which the liquid nitrogen during the respective regeneration phase from the adsorption traps into one as well not shown storage vessel is pressed. After the respective regeneration this liquid nitrogen is then pumped back into the respective adsorption trap.

The actual regeneration process can also be different Way. One possibility is - as shown - to evaporate Heat up nitrogen and flow through the trap to be regenerated permit. For this purpose, part of the through the cooler or the cooling rod 3 of the cooling stage 2 flowing nitrogen gases via the line 73, the feed pump 74, the electric heater 75 and the lines 76 and 77 with the valves t8 and 79 behind the valves 48, 49 supplied to the product gas feed lines. Are during regeneration the valves 48, 57 and 49, 58 are closed. Via the lines 81 with the valves 82, 83, which are each open during the regeneration phase, the regeneration gases flow the end. The regeneration gas temperature is expediently approx. 400 K.

Another way of regenerating the activated carbon or the Molecular sieve in the adsorption traps 51, 52 consists in the containers 53, 54 to arrange a heating rod or to heat the container outside and the heater to bring about a sufficiently high temperature during the respective regeneration phase with simultaneous evacuation with vacuum pump 89. With this version, on the The supply and heating of nitrogen as a regeneration gas can be dispensed with.

After the desorption process, the valves 78, 82 and

79, 83 closed and the lines 55, 56 via the lines 85, 86 connected valves 87, 88 open. These lead to a vacuum pump 89, with the first of all regenerated containers 53 or 54 at one pressure is evacuated from approx. 10 mbar. Only then is the liquid filled in Nitrogen, either from the storage container 13 or, as described, but not shown, from a further storage container, into which the liquid nitrogen beforehand of the respective liquid bath was pressed.

The low-pressure process described here can also be used with higher operating pressures operated as 10 to 50 bar, e.g. B. with operating pressures of 150 to 250 bar. When operating with such high operating pressures, the condensation can be connected to the downstream Adsorption stages can either be dispensed with entirely or the traps can be substantial be built smaller in their adsorber dimensions.

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Claims (27)

Method and device for separating hydrogen or helium from gas mixtures. REQUIREMENT 2 Process for the separation of hydrogen or helium from gas mixtures using a cooling stage system, where in the mixture the gas to be separated as well as nitrogen, oxygen and / or gases from about the same Boiling range are included, that is, that the Gas mixture in at least two, preferably three cooling stages (2, 6, .15) to approx. 60 is cooled down to 70 K for the purpose of condensation of the higher-boiling gases. 2. The method according to claim 1, d a d u r c h g e k e n n -z e i c h n e t that the condensation of the higher boiling gases at an operating pressure of 150 to 250 bar. 3. The method according to claim 1, d a d u r c h g e k e n n -z e i c h n e t that the condensation of the higher boiling gases at an operating pressure of 10 to 50, preferably 20 bar and that the remaining gas mixture in a downstream adsorption trap (53, 54) is subjected to fine cleaning. 4. The method according to any one of claims 1, 2 or 3, d a d u r c h it is noted that the starting gas mixture is in a first cooling stage (2) is cooled to 100 to 130 K in countercurrent with the end products obtained. 5. The method according to any one of the preceding claims, d a d u r c h e k e k e n n n e i c h n e t that the starting gas mixture in two (further) cooling stages is cooled to 60 to 70 K, preferably 63 K, with LN2 baths. 6. Device for performing one of the methods according to the preceding Claims, d u r c h e k e n n -z e i c h n e t, that two or three cooling stages (2, 6, 15) are provided, which are designed such that the temperature of the Product gas in the last stage is 60 to 70 K, preferably 63 K. 7. Apparatus according to claim 6, d a d u r c h g e k e n z e i c h n e t that three cooling stages (2, 6, 15) are provided. 8. Apparatus according to claim 7, d a d u r c h g e k e nt z e i c h n e t that the first cooling stage (2) is designed as a countercurrent cooler. 9. Apparatus according to claim 7 or 8, d a d u r c h g e k e n n z e i c h n e t that the second and third stage <6 ,. 15) Dewar vessels with these each penetrating cooling coils (7, 19) comprises. 10.Vorrichtung according to claim 9, d a d u r c h g e k e n n. z e i c h n e t that the cooling stage (15) has a storage container (21) for condensed gases is connected downstream. 11.Vorrichtung according to claim 10, d a d u r c h g e k e n n z e i c h n e t that a further storage container (29) fed by the storage container (21) is provided. 12.Vorrichtung according to claim 11, d a d u r c h g e k e n n z e i c h n e t,. that the storage container (29) with the cooling stages (6, 15) via supply lines (31) are connected to one another with valves (33, 35). 13.Vorrichtung according to claim 12, d a d u r c h g e k e n n z e i c h n e t that the storage tank (29) and the LN2 bath of the cooling stage (15) level sensor (34, 32) are assigned. 14. The apparatus of claim 13, d adurch g e k e n n z e i c h n e t that the supply of the cooling stage (15) depends on the level sensor (32) takes place while the cooling stage (6) is being supplied depending on the level sensor (34) takes place. 15. Device according to one of claims 9 to 14, d a d u r c h g e k e n n n n e i n e t that the cooling stages (6 and 15) level sensors (11) and (41) are assigned to the refrigerant supply with the help of valves (12) and (42) serve from another storage tank (13). 16. Device according to one of claims 7 to 15, d a d u r c h g It is not noted that the cooling stage (15) is in a cold-insulated box (44) is housed. 17. The device according to claim 16 and one of claims 11 to 14, d a d u r c h e k e n n n z e i c h n e t. that the storage container (21) and (29) are housed in the cold box (44). 18. The apparatus of claim 16 or 17, d a d u r c h g e k e n It is noted that a vacuum pump (45, 46) is connected to the interior of the cold box is. 19. The apparatus of claim 18, d a d u r c h g e k e n n z e i c h n e t that the insulating space (10) of the Dewar vessel of the cooling stage (6) with the Inside the cold box (44) is connected. 20. Device according to one of claims 9 to 19, d a d u r c h g e k e n n n n e i c h n e t that the third cooling stage (15) from a vessel (16) with a central insert (17) is formed. 21. The device according to claim 20, d a d u r c h g e k e n n z e i c h n e t that the annular space (18) formed by the central insert (17) the contains liquid refrigerant and the cooling coil (19). 22. The device according to claim 20 or 21, d a d u r c h g e k e n It is not indicated that the central insert (17) flows through from bottom to top and is filled with packing. 23. Device according to one of claims 6 to 22, d a d u r c h g It is not noted that the cooling stage (15) is followed by adsorption traps (51, 52) are. 24. The device according to claim 23, d a d u r c h g e k e n n z e i c h n e t that the adsorption traps (51, 52) container (53, 54) with the adsorbent have, which are arranged in Dewar vessels. 25. The device according to claim 24, d a d u r c h g e k e n n z e i c h n e t that the adsorption traps (51, 52) are equipped with heating devices (68, 69) are. 26. The device according to claim 24, d a d u r c h g e k e n n z e i c h n e t that the adsorption traps (51, 52) an electric heater (75) for the Supply of hot regeneration gases is assigned. 27. Device according to one of claims 23 to 26, d a d u r c h it is noted that the adsorption traps (51, 52) have a Line system connected to the last cooling stage (15) and other facilities is that alternate operation is possible.